Heretofore, in the operation of cooking griddles, the griddle temperature control means employed was not of sufficient sensitivity to the actual griddle plate temperature to prevent a high-low plate temperature range of less than about 15 to 20 degrees F. which required a considerable expense of heating energy to bring the plate temperature to the preferred working condition, and maintain it under load, once the plate temperature dropped during the "off" portion of the heating cycle. A much lower "on-off", or "high-low" temperature range of the cooking medium is desired, to save both heating energy and operating time. Prior attempts to solve that problem are exemplified by Pat. Nos. 2,846,147 and 3,511,971, for deep fat fryers and griddle plate, respectively, and the present invention is intended to be an improvement over the principles utilized in the said prior patents.